1. Technical Field
Embodiments of the present invention relate to a method of preparing an immobilized core-shell copper nanoparticle catalyst which can be used as a catalyst in a cross-coupling reaction between a chalcogenide precursor compound and a boron-containing compound, thereby achieving high yield and selectivity, and which is cost-effective because it can be recovered and recycled, and to a cross-coupling reaction between a chalcogenide precursor compound and a boron-containing compound, which is performed using the copper nanoparticle catalyst.
2. Description of the Related Art
Over the past few years, metal nanoparticles have been used in various fields including medicines, materials, environment, energy, etc. Unlike conventional bulky metal materials, these metal nanoparticles have exhibited high reactivity with various molecules due to their large surface areas. In various industrial chemistry fields, the cost effectiveness and environmental friendliness of metal nanocatalysts have become important, and thus it has become important to recycle highly toxic catalysts. In connection with this, many documents have reported the immobilization of metal nanoparticles on various supports, such as charcoal, alumina, porous silica materials, etc. Such metal nanoparticles immobilized on solid supports can be easily recycled and have high reactivity and dispersibility.
Meanwhile, many studies on materials with carbon-selenium bonds have been conducted due to their antimicrobial activity, anticancer activity and antioxidant activity. In addition, a selenium-based ionic liquid is an effective catalyst in the carbonylation of aniline, the oxidation of thiol, and the synthesis of thioacetals and octahydroacridines. For the past few years, studies on new methods for the synthesis of organochalcogens based on sp3, sp2 and sp carbon atoms and selenium or tellurium have been conducted. For the synthesis of these chalcogenides, many methods have been reported, and as an example, methods that use diphenyl diselenide or diphenyl ditelluride as a precursor have been used due to their air stability, environmental friendliness, and industrial applicability. Diphenyl diselenide can react with aryl halides or organic boronic acid to synthesize organochalcogen derivatives. Herein, organic boronic acid and its esters are stable and less toxic, and thus can be industrially used together with various reactants. For this reason, a coupling reaction between diphenyl diselenide and organic boronic acid is useful in the synthesis of asymmetric organochalcogen compounds.
Meanwhile, the use of inexpensive and toxic copper catalysts in catalytic reactions is not preferable in terms of cost effectiveness and efficiency. In recent years, some documents have reported synthesizing aryl selenides using copper salts in the presence of ligands and other additives under the conditions of long reaction time, high temperature and high catalyst loading.
As an example, a document reported the synthesis of diaryl selenide and telluride from aryl boronic acid in the presence of CuI as a catalyst. A representative study thereon was disclosed in L. Wang, M. Wang, and F. Huang, Synlett 2005, 13, 2007-2010. In addition, methods that use CuI and bipyridyl ligand to synthesize various asymmetric organochalcogen compounds were reported. A representative study thereon was disclosed in N. Taniguchi, J. Org. Chem. 2007, 72, 1241-1245. Furthermore, the cross-coupling reaction of diaryl diselenide, which uses glycerol as an environmentally friendly solvent and CuI as a catalyst, was reported. A representative study thereon was disclosed in D. Alves, C. G. Santos, M. W. Paixao, L. C. Soares, D. Souza, O. E. D. Rodrigues, and A. L. Braga, Tetrahedron Lett. 2009, 50, 6635-6638. In addition, the synthesis of diphenyl chalcogenide using a copper salt as a catalyst in the presence of a base, a ligand and a reducing agent was also reported. A representative study thereon was disclosed in A. Kumar, and S. Kumar, Tetrahedron 2014, 70, 1763-1772.
The methods using metal salts as disclosed in the above-described prior art documents are performed under homogeneous conditions, and thus have difficulty in the recovery and recycle of catalysts. This increases the synthesis cost and limits the applicability of the reaction. Therefore, there has been a need to develop a catalyst system which is applicable to various functional groups and which does not require a base, a reducing agent or other additives.